1. Field of the Invention
The present invention relates to a method and apparatus for measuring the density of bones. More specifically, it relates to a method and apparatus for measuring bone mineral mass using radiographic absorptiometry.
2. Background of the Invention
Osteoporosis is a bone disease characterized by low bone mass and microarchitectural deterioration of bone tissue. This disease subjects a person to enhanced bone fragility and a consequent increase in fracture risk, particularly in the spine, hip and wrist. Osteoporosis is particularly common in postmenopausal women because their bone loss greatly exceeds that of men at this age. It has been estimated that at least 28 million Americans, 80% of whom are women, have a lower than normal bone mass and are at risk of having osteoporosis. In the United States alone, 10 million people already have osteoporosis and many women die each year from complications due to osteoporosis.
The assignee of the present invention has developed a proprietary bone density measurement system called OsteoGram Analysis. The OsteoGram Analysis system involves taking a standard X-ray of three fingers, along with a calibration wedge in the field of view by using existing and widely available standard X-ray equipment. The calibration wedge is utilized to adjust for differences among X-ray equipment, exposures, types of film, and the development process. The assignee of the present invention has a central specialized laboratory that receives these x-rays and provides a service to medical professionals of providing a bone mineral density (BMD) report based on the x-ray.
Although this service provides accurate reports, there has been a demand for an on-site solution that can be utilized by physicians or other medical professionals locally at their offices to generate the BMD report based on hand x-rays. Unfortunately, such a solution must overcome many difficult challenges, described below. Although there are piece-meal attempts to develop such a solution (see, e.g., U.S. Pat. Nos. 5,712,892 and 5,696,805), a complete solution has not been developed and has been elusive until now.
The first challenge is that the hardware needs to be simplified and reduced in cost, yet provide the same level of accuracy as the specialized custom hardware of the central laboratory. For example, the U.S. Pat. No. 5,712,892 utilizes CCD photodetector arrays to digitize the radiograph. The digitization results are excellent. However, it is cost prohibitive as an on-site solution and requires additional equipment to keep the arrays cool.
The second challenge is to develop new software that does not require the intervention and judgment of a trained technician. The equipment for the OsteoGram service is typically complex, and the intermediate segmentation results must be interpreted and verified by a skilled person (e.g., a laboratory technician with specialized training). The requirement of a trained technician results in added costs to train and employ these technicians. It is certainly cost prohibitive for each medical professional to hire a technician to work in their office.
The third challenge is to develop an easy-to-use graphical user interface that is intuitive, easy to learn, and that requires minimal set-up and learning time. For example, the U.S. Pat. No. 5,696,805 does not provide any graphical user interfaces, nor does it even allow for user input. In fact, it appears that the method of U.S. Pat. No. 5,696,805 does not even display the contours to the user, but instead the figures of this patent merely illustrate output data results from screen dumps of an image at pre-determined points in the program only to show a proper execution of the program.
The fourth challenge is to generate the BMD in a timely manner so that a medical professional can provide a report of the results in a matter of a few minutes while the patient is still in the office. As a point of comparison, the processing that occurs in the central laboratory can take more than half an hour of processing time in addition to time needed by a technician to verify and correct the output or otherwise aid the system. Only then can results be sent back to the client.
Accordingly, it would be advantageous to have a solution that makes BMD testing and report as simple as taking a patient's temperature or blood pressure reading. No previous systems exist, however, that can provide a measure of bone density with minimum human intervention by simply scanning in an x-ray with a desktop scanner and running a program with an easy-to-use and intuitive graphical user interface on a personal computer (PC).
Other Bone Assessment Devices
Various devices for measuring the content of bone have been known for a number of years, and by way of example, several forms of these devices can be found in U.S. Pat. Nos. 5,712,892, 5,785,656, and 5,917,877. U.S. Pat. No. 5,785,656 is directed towards a bone assessment device that utilizes ultrasound technology. Although this technology has potential for providing bone mass measurements, it has not matured and faces several un-resolved technical hurdles. For example, it is yet to be determined which features of ultrasound velocity and attenuation are related to bone density, which features of velocity and attenuation reflect bone architecture, and how these features can be combined to estimate bone mass.
U.S. Pat. Nos. 5,712,892 and 5,917,877 are directed towards bone measurement devices that utilize an X-ray beam for acquiring data. Unfortunately, these devices are complex to implement, costly to manufacture, and generally require substantial training before users can competently operate the devices.
Accordingly, there remains a need for an improved method and apparatus for generating a bone mineral density report based on a radiograph of a patient's hand that departs significantly from existing systems.